EFI On Motercycles

Tony Cooper tony.cooper at virgin.net
Wed Nov 12 11:11:59 GMT 1997


Terry Sare wrote:
> 
>      I didn't post to efi but am curious about efi on motorcycles. I have a
>      600cc Honda Hurricane motor that I want to efi.
> 
> 
>      1. Would a Holly 4 (650CFM) barrel TBI work or is it to big CFM wise.
> 
>      2. Something better -- what CFM rate does it require? (Under 10k RPM);
> 
> 
> 
>      Thanks
> 
>      Terry Sare

Hi Terry,

It is very difficult to give an exact CFM requirment on a given engine
without experiments, but the following may help.

The formula 
		    D*rpm*VE
		cfm=--------
		     345600

Where:-		D=engine displacement in Cu.in
		rpm=engine rpm at maximum horsepower
		VE=volumetric efficency at maximum horsepower

As the honda engine could almost be construed to be a racing engine
(bike engines usually are...!!!), you can take the VE to be approx 90%,
with a maximum horsepower @ 8000 RPM (guestimate). Feeding these values
into the formula gives
76.27 CFM at maximum power.

As you can see this may be a little small for a 650 CFM Holly!!!

Another suggestion, is use an inlet stack from a Kawasaki GPZ750 Turbo.
It has injectors already fitted, with a throttle pot fitted to the end
of the throttle spindle.

It will do the job for you (The two engine power outputs are
approximatly the same!)

Hope this helps
TTFN
Tony


-- 
Sent By Tony Cooper.
email: tony.cooper at virgin.net
Allow at least 10 working minutes for reply. ;)




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